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double-filter. The clear filtrate is concentrated on the water-
bath until crystallisation commences and allowed to cool.
The crystals of the hydrochloride of phenylenecliamine sepai'ate
and are filtered, A further quantity may be obtained by con-
centrating the mother-liquors. Yield 6*5 grams,

Reaction.  Dissolve a few crystals in water, acidify with
dilute hydrochloric acid, and add a drop of sodium nitrite solu-
tion. A deep brown solution (Bismarck brown) is obtained.
See Appendix, p. 279,

;                                                           PREPARATION 59,
Dimethylaniline, C0HflN(CH3)3
Poirrier, Chappat,./a/jm&, 1866, p. 903,
20 grms. aniline hydrochloride,
15         aniline.
22        methyl alcohol.
The aniline hydrochloride is prepared by gradually ad.cling"
cone,   hydrochloric  acid to aniline  (20  grams  in a beaker)
until a drop brought on to a piece of filter paper, stained with
:                           methyl violet, turns it green.    The liquid is quickly cooled   and
stirred so as to produce small crystals.    It is then filtered, well
;                           pressed and dried on a porous plate.    The dry hydrochloride is
'       ,                     brought into a thick-walled tube closed at one  end, and   the
mixture of aniline and methyl alcohol added.    The tube is   then
;                           sealed  in the  ordinary way  and heated in the tube furnace
i                           gradually to 150 during two hours, and then to 180200 for
j                           six hours  more.    The contents  of the  tube  divide  into    two
I                               layers, the lower one consisting of the  hydrochloride  of   the
J                           base and water, and the upper one of the free bases.   The whole
j                            of the contents are poured out into a large separating funnel,
;|                            and caustic soda added in excess.   The addition of a little ether
II                              causes the bases to separate out more readily.    The top layei*
f!    I                      is removed, and the lower aqueous portion is shaken up  twice: